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The intelligent traffic signal control aims at optimization of time spent at any intersection by the visiting vehicular traffic. The parameters considered are the mass density of the traffic on each leaf of the intersection and waiting time at each signal. Consider the following two cases:
Case 1: An intersection with equal flow of traffic in all directions.
This represents a theoretical case as the present design scenario of any metropolitan indicates that traffic depends not only on the density of population inhabiting it but, also on the usage of roads and highways and also the time of the day. Equal flow implies that the time allotted to each signal for clearance of traffic on its side can be set as same. The time can vary, but, equally for all sides, according to the decent time requirements for that specific road. An example of such an intersection could be taken to be any one on the roads which do not lie on the main road or national highways.
Let the mass density on leaf 1 be m1 vehicles/m2 and the time the signal is on be t1 sec.
Let the mass density on leaf 2 be m2 vehicles/m2 and the time the signal is on be t2 sec.
Let the mass density on leaf 3 be m3 vehicles/m2 and the time the signal is on be t3 sec.
Let the mass density on leaf 4 be m4 vehicles/m2 and the time the signal is on be t4 sec.
This case represents the condition wherein
m1=m2=m3=m4=m
i.e. t1=t2=t3=t4=t
The time t can be chosen to clear a certain block of traffic which can be chosen in accordance to the amount of traffic that frequents that intersection. Here in optimization of time is achieved by choosing the minimum block.
Case 2:
In practice, such a scenario does not occur on most frequented roads as the flow on these is in one direction only. As such consider the case when the following conditions exist:
m1>m2=m3=m4.
Now if t1=t2=t3=t4,
Then the time for which the signal stays on would be according to the highest mass density i.e. m1, so as to make it possible for maximum traffic to be cleared at one time and prevent clogging of road. Let us say that the number of vehicles cleared in that time be x. In most of the practical situations, the traffic on the lower density leaf is less than x.
intersection and faster flow.
WORKING
The main modules for the project are as follows:
- Power Supply
- Control Units
- Sensing unit ( For each site)
Display unit ( For Signals) According to the input from site having maximum density. We can also set the control unit to serve the site according to the priority basis for each site.Our Intruder circuit will act as traffic density sensor at four ends.
It consists of following parts
- ELECTRO-OPTICAL CONVERTER:
This module converts the electrical signal into light signal, which are transmitted through Infrared Rays or wireless communication. In a light source forms the carrier and must also be modulated to transmit information. Usually the transmitter simply turns the light source on and off.
- OPTICAL TO ELECTRIC CONVERTER:
To decode the information from the light pulses, some type of light detector must be employed. The detector's job is to convert the light signals, collected at the receiver, into electrical signals. It is the intensity or power of the light that determines its strength. Therefore, the real job of the light detector is to convert light power into electrical power, independent of the energy of the transmitted light pulses. This relationship also implies that the conversion is independent of the duration of the light pulses used.
Microcontrollers for embedded systems
In the literature discussing microprocessors, we often see a term embedded system. Microprocessors and microcontrollers are widely used in embedded system products. An embedded product uses a microprocessor (or microcontroller) to do one task and one task only. A printer is an example of embedded system since the processor inside it performs one task only: namely, get data and print it. Contrasting this with IBM PC which can be used for a number of applications such as word processor, print server, network server, video game player, or internet terminal. Software for a variety of applications can be loaded and run. Of course the reason a PC can perform myriad tasks is that it has RAM memory and an operating system that loads the application software into RAM and lets the CPU run it. In an embedded system, there is only one application software that is burned into
For step down transformer, N1>N2, i.e., numbers of turns of primary winding is more than those in secondary.
· SENSORS
A sensor is a type of transducer, or mechanism, that responds to a type of energy by producing another type of energy signal, usually electrical. They are either direct indicating (an electrical meter) or are paired with an indicator (perhaps indirectly through an analog to digital converter, a computer and a display) so that the value sensed is translated for human understanding. Types of sensors include electromagnetic, chemical, biological and acoustic. Aside from other applications, sensors are heavily used in medicine, industry and robotics.
In order to act as an effectual sensor, the following guidelines must be met:
- the sensor should be sensitive to the measured property
- the sensor should be insensitive to any other property
- the sensor should not influence the measured property
In theory, when the sensor is working perfectly, the output signal of a sensor is exactly proportional to the value of the property it is meant to measure. The gain is then defined as the ratio between output signal and measured property. For example, if a sensor measures temperature and has an actual voltage output, the gain is a constant with the unit.
When the sensor is not perfect, various deviations can occur, including gain error, long term drift, and noise. These and other deviations can be classified as systematic, or random, errors. Systematic deviations may be compensated for by means of some kind of calibration strategy. Noise is an example of a random error that can be reduced by signal processing, such as filtering, usually at the expense of the dynamic behavior of the sensor.
· TRANSFORMER
Transformer works on the principle of mutual inductance. We know that if two coils or windings are placed on the core of iron, and if we pass alternating current in one winding, back emf or induced voltage is produced in the second winding. We know that alternating current always changes with the time. So if we apply AC voltage across one winding, a voltage will be induced in the other winding. Transformer works on this same principle. It is made of two windings wound around the same core of iron. The winding to which AC voltage is applied is called primary winding. The other winding is called as secondary winding.
Voltage and current relationship:
Let V1 volts be input alternating voltage applied to primary winding. I1 Amp is input alternating current through primary winding. V2 volt is output alternating voltage produced in the secondary. I2 amp be the current flowing through the secondary.
Then relationship between input and output voltages is given by
V1/V2 = N1/N2
Relationship between input and output currents is
I1/I2 = N2/N1
(Where N1 is no. of turns of coil in primary and N2 is number of turns in secondary )
We know that Power = Current X Voltage. It is to be noted that input power is equal to output power. Power is not changed. If V2 is greater than V1, then I2 will be less than I1. This type of transformer is called as step up transformer. If V1 is
greater than V2, then I1 will be less than I2. This type of transformer is called as step down transformer.
For step up transformer, N2>N1, i.e., number of turns of secondary winding is more than those in primary.
MICROCONTROLLERS FOR EMBEDDED SYSTEMS
In that they remain code compatible with the 8051. This has led to many versions of the 8051 with different speeds and amount of on-chip ROM marketed by more than half a dozen manufacturers. It is important to know that although there are different flavors of the 8051, they are all compatible with thin the literature discussing microprocessors, we often see a term embedded system. Microprocessors and microcontrollers are widely used in embedded system products. An embedded product uses a microprocessor (or microcontroller) to do one task and one task only. A printer is an example of embedded system since the processor inside it performs one task only: namely, get data and print it. Contrasting this with a IBM PC which can be used for a number of applications such as word processor, print server, network server, video game player, or internet terminal. Software for a variety of applications can be loaded and run. Of course the reason a PC can perform myriad tasks is that it has RAM memory and an operating system that loads the application software into RAM and lets the CPU run it. In an embedded system, there is only one application software that is burned into
Although microcontrollers are the preferred choice for many embedded systems, there are times that a microcontroller is inadequate for the task. For this reason, in many years the manufacturers for general-purpose microprocessors have targeted their microprocessor for the high end of the embedded market.
INTRODUCTION TO 8051
In 1981, Intel Corporation introduced an 8-bit microcontroller called the 8051. This microcontroller had 128 bytes of RAM, 4K bytes of on-chip ROM, two timers, one serial port, and four ports (8-bit) all on a single chip. The 8051 is an 8-bit processor, meaning the CPU can work on only 8- bit pieces to be processed by the CPU. The 8051 has a total of four I/O ports, each 8- bit wide. Although 8051 can have a maximum of 64K bytes of on-chip ROM, many manufacturers put only 4K bytes on the chip.
The 8051 became widely popular after Intel allowed other manufacturers to make any flavor of the 8051 they please with the conditioe original 8051 as far as the instructions are concerned. This means that if you write your program for one, it will run on any one of them regardless of the manufacturer. The major 8051 manufacturers are Intel, Atmel, Dallas Semiconductors, Philips Corporation, Infineon.
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